In recent years there has been an ever increasing trend towards safer and sustainable detergent compositions. This has led to the development of alternative complexing agents, builders, threshold agents, corrosion inhibitors, and the like, which are used instead of predominantly phosphorus containing compounds. Phosphates can bind calcium and magnesium ions, provide alkalinity, act as threshold agents, and protect alkaline sensitive metals such as aluminum and aluminum containing alloys.
Alkaline detergents, particularly those intended for institutional and commercial use, generally contain phosphates, nitrilotriacetic acid (NTA) or ethylenediaminetetraacetic acid (EDTA) as a sequestering agent to sequester metal ions associated with hard water such as calcium, magnesium and iron and also to remove soils. In particular, NTA, EDTA or polyphosphates such as sodium tripolyphosphate and their salts are used in detergents because of their ability to solubilize preexisting inorganic salts and/or soils. When calcium, magnesium salts precipitate, the crystals may attach to the surface being cleaned and cause undesirable effects. For example, calcium carbonate precipitation on the surface of ware can negatively impact the aesthetic appearance of the ware, giving an unclean look. The ability of NTA, EDTA and polyphosphates to remove metal ions facilitates the detergency of the solution by preventing hardness precipitation, assisting in soil removal and/or preventing soil redeposition during the wash process.
While effective, phosphates and NTA are subject to government regulations due to environmental and health concerns. Although EDTA is not currently regulated, it is believed that government regulations may be implemented due to environmental persistence. There is therefore a need in the art for an alternative, and preferably environment friendly, cleaning composition that can reduce the content of phosphorus-containing compounds such as phosphates, phosphonates, phosphites, and acrylic phosphinate polymers, as well as persistent aminocarboxylates such as NTA and EDTA.
In addition, environmentally-friendly detergent compositions still have to be effective and capable of removing difficult soils, especially those found in institutional settings such as restaurants. In particular, detergent compositions have to remove protein soils, starchy or sugary soils, fatty soils, and the like, where the soil may be burnt or baked on or otherwise thermally degraded.
There is a need for alternative, effective cleaning compositions.
Accordingly, it is an objective of the claimed invention to develop phosphorus-free acid compositions for use in an alternating alkali/acid system for warewashing.
A further object of the invention is to provide phosphorus-free acid products that outperform phosphoric acid, including for example urea sulfate and citric acid.
A further object of the invention is to provide improved methods for use in an alternating alkali/acid system for warewashing, including for example, providing excellent cleaning and rinsing results through the use of a single product for the acid shock treatment step and the final rinse step (rinse-aid).
A further object of the invention is improved residual acid in a rinse application of an alternating alkali/acid warewashing system.